1. Field of the Invention
This invention relates to a novel apparatus for continuously pickling the outer circumferential surfaces of tubular members, for example, zircaloy tubes adapted to clad nuclear fuel.
2. Description of the Prior Art
In order to obtain products of a metallic raw material of the same type as zircaloy, it is necessary, as well-known in the case of tubes made of, for example, zirconium or a zirconium alloy, to subject the inner and outer surfaces of the tubes to a pickling treatment using an acidic solution such as nitric acid or the like so as to obtain a mirror-finished surface after carrying out their final annealing step and then polishing only the outer surfaces of the tubes. Where such tubes are intended for use in cladding nuclear fuel, a particularly severe quality control is required and special care must be taken when pickling both inner and outer surfaces of the tubes.
With a view toward fulfilling such a severe requirement for high quality, the present assignee previously developed an apparatus for continuously pickling the outer surfaces of tubular materials as disclosed in Japanese Patent Publication No. 39629/1980. Although the superiority and industrial utility of the above-mentioned apparatus have been proven in the field of the present art, it has been found that the quality of the surface of a pickled tube is considerably affected by the degree of cleanliness of the surface of the tube prior to the pickling treatment and, where the surface before the pickling treatment is contaminated with oil, grease or dust, such a contaminant would become a serious cause for developing surface irregularities such as pits or the like.